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"The new gearbox fits into the existing space for the legacy component and provides for increased time between overhaul interval of up to 25 percent. The extra weight of the new gearbox is offset with weight savings elsewhere on the aircraft. Sikorsky has both ground tested and flight tested the new gearbox.
During ground testing, the gearbox ran for more than seven hours and the test was halted only when the engineers got to the time when the helicopter would have run out of a full load of fuel. The new “Phase IV” gearbox was also flown for more than 200 flight hours and also later torn down and inspected in the presence of the FAA.
Notably, the design uses a supplemental fuel pump and additional oil lines to reuse main gearbox oil that is accumulated in a lower sump in the event of primary lubrication failure. While some other OEMs have developed “run dry” gearboxes that can function for between 30 and 50 minutes without primary lubrication, Sikorsky found this of dubious value given the offshore distances some of its customers must fly.
When secondary lubrication kicks in, the event generates a “technical indicator” back to Sikorsky to facilitate troubleshooting once the impacted helicopter lands or returns to base. Brady said customers greeted the new gearbox enthusiastically and want it “as soon as possible.”
The new gearbox can be fitted to existing helicopters as part of the current 1,500-hour inspection, she said, and is just one of several menu items that can be selected for the A+ upgrade. Other options under the upgrade include an increased gross weight kit to 27,700 pounds and an uprated engine, the GE CT7-8A6, that offers better payload capability and high and hot performance. The new engine, which was certified in June, allows customers to operate with both full seats and full fuel under most conditions."